Methods and system for estimating a temperature of an after treatment device

ABSTRACT

Systems and methods for estimating a temperature of an after treatment device in an exhaust system of an engine are described. In one example, the temperature is estimated during condition when an engine is in a fuel cut-out mode and fuel vapors are being released to the engine via a fuel vapor storage canister.

FIELD

The present description relates to methods and a system for estimating atemperature of an after treatment device and adjusting operation of avehicle responsive to the temperature. The methods and systems may beparticularly useful for vehicles that may include a fuel vaporcollection and purging system.

BACKGROUND AND SUMMARY

A vehicle may include an after treatment device for processing exhaustgases of an engine. The after treatment device may oxidize some exhaustgas constituents and reduce other exhaust gas constituents. The aftertreatment device may be initially heated via exhaust gases. Once itreaches a light off temperature, the after treatment device may reachtemperatures that may be higher than exhaust gas temperatures. Inparticular, hydrocarbons entrained in the exhaust gases may be combustedwithin the after treatment device so as to raise a temperature of theafter treatment device. The temperature of the after treatment devicemay be increased or decreased via controlling amounts of oxygen andhydrocarbons that are present in the engine's exhaust gases. Operatingthe after treatment device at temperatures that are higher than athreshold temperature may result in a loss of after treatment deviceefficiency. Therefore, it may be desirable to accurately determine atemperature of the after treatment device. Nevertheless, installingtemperature sensors in the after treatment device may be costprohibitive.

The inventors herein have recognized the above-mentioned issues and havedeveloped an engine operating method, comprising: operating an engine ina fuel cut-out mode wherein the engine rotates without injecting fuel tothe engine via fuel injectors; delivering fuel to the engine via a fuelvapor canister while operating the engine in the fuel cut-out mode; andestimating a temperature of an exhaust after treatment device via acontroller, the controller estimating the temperature of the exhaustafter treatment device based on combusting fuel supplied from the fuelvapor canister in the exhaust after treatment device while operating theengine in the fuel cut-out mode.

By estimating a temperature of an after treatment device while an engineis operating in a fuel cut-out mode, it may be possible to maintain atemperature of the after treatment device below a threshold temperature.In one example, flow through a canister purge valve may be reduced inresponse to the estimated temperature of the after treatment device sothat the temperature of the after treatment device may be maintainedbelow the threshold temperature. In this way, it may be possible toreduce an amount of fuel vapor stored in a fuel vapor canister so thatfuel vapors may not be released to atmosphere while at the same timepreserving efficiency of an after treatment device.

The present description may provide several advantages. In particular,the approach may preserve after treatment device efficiency. Inaddition, the approach may reduce fuel vapors that are stored in a fuelvapor storage canister so that the fuel vapors may not be released toatmosphere. Further, the approach may provide an improved temperatureestimate of an after treatment device.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of an engine;

FIG. 2 is a schematic diagram of an evaporative emissions system;

FIGS. 3A-3C is a flowchart of an example method for estimating atemperature of an exhaust after treatment device;

FIG. 4 shows an example engine operating sequence that includes purgingfuel vapors from a fuel vapor storage canister;

FIG. 5 shows an example engine operating sequence that includesreactivating an exhaust after treatment to improve reduction of NOx; and

FIG. 6 shows an example fuel cloud that may develop in an exhaustsystem.

DETAILED DESCRIPTION

The present description is related to estimating a temperature of anexhaust after treatment device. The temperature of the exhaust aftertreatment device may be determined when purge fuel vapors are flowing toan engine operating in a fuel cut-out mode and when the after treatmentdevice is being reactivated after exiting fuel cut-out mode. The enginemay be of the type shown in FIG. 1. The engine may periodically receivefuel vapors from an evaporative emissions system as shown in FIG. 2. Amethod for estimating a temperature of an after treatment device andoperating an engine is shown in FIGS. 3A-3C. An example engine operatingsequence in which a temperature of an exhaust after treatment device isestimated while the engine operates in fuel cut-out mode is shown inFIG. 4. Another example engine operating sequence is shown in FIG. 5where a temperature of the exhaust after treatment device is estimatedwhile the exhaust after treatment is being reactivated. A graphicdepiction of a fuel cloud within an exhaust system is shown in FIG. 6.

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. The controller 12receives signals from the various sensors shown in FIGS. 1 and 2. Thecontroller may employ the actuators shown in FIGS. 1 and 2 to adjustengine operation based on the received signals and instructions storedin memory of controller 12.

Engine 10 is comprised of cylinder head 35 and block 33, which includecombustion chamber 30 and cylinder walls 32. Combustion chamber 30 mayalternatively be referred to as a cylinder. Piston 36 is positionedtherein and reciprocates via a connection to crankshaft 40. Flywheel 97and ring gear 99 are coupled to crankshaft 40. Optional starter 96(e.g., low voltage (operated with less than 30 volts) electric machine)includes pinion shaft 98 and pinion gear 95. Pinion shaft 98 mayselectively advance pinion gear 95 to engage ring gear 99 and crankshaft40. Ring gear 99 is directly coupled to crankshaft 40. Starter 96 may bedirectly mounted to the front of the engine or the rear of the engine.In some examples, starter 96 may selectively supply torque to crankshaft40 via a belt or chain. In one example, starter 96 is in a base statewhen it is not engaged to the engine crankshaft 40.

Combustion chamber 30 is shown communicating with intake manifold 44 andexhaust manifold 48 via respective intake valve 52 and exhaust valve 54.Each intake and exhaust valve may be operated by an intake cam 51 and anexhaust cam 53. The position of intake cam 51 may be determined byintake cam sensor 55. The position of exhaust cam 53 may be determinedby exhaust cam sensor 57. Intake valve 52 may be selectively activatedand deactivated by valve activation device 59. Exhaust valve 54 may beselectively activated and deactivated by valve activation device 58.Valve activation devices 58 and 59 may be electro-mechanical devices.

Fuel injector 66 is shown protruding into combustion chamber 30 and itis positioned to inject fuel directly into cylinder 30, which is knownto those skilled in the art as direct injection. Fuel injector 66delivers liquid fuel in proportion to the pulse width from controller12. Fuel is delivered to fuel injector 66 by a fuel system (not shown)including a fuel tank, fuel pump, and fuel rail (not shown). In oneexample, a high pressure, dual stage, fuel system may be used togenerate higher fuel pressures.

In addition, intake manifold 44 is shown communicating with turbochargercompressor 162 and engine air intake 42. In other examples, compressor162 may be a supercharger compressor. Shaft 161 mechanically couplesturbocharger turbine 164 to turbocharger compressor 162. Electronicthrottle 62 adjusts a position of throttle plate 64 to control air flowfrom compressor 162 to intake manifold 44. Pressure in boost chamber 45may be referred to a throttle inlet pressure since the inlet of throttle62 is within boost chamber 45. The throttle outlet is in intake manifold44. In some examples, throttle 62 and throttle plate 64 may bepositioned between intake valve 52 and intake manifold 44 such thatthrottle 62 is a port throttle. Compressor recirculation valve 47 may beselectively adjusted to a plurality of positions between fully open andfully closed. Waste gate 163 may be adjusted via controller 12 to allowexhaust gases to selectively bypass turbine 164 to control the speed ofcompressor 162. Air filter 43 cleans air entering engine air intake 42.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of exhaust gas after treatment device 70.Alternatively, a two-state exhaust gas oxygen sensor may be substitutedfor UEGO sensor 126. Flange 160 allows exhaust manifold 48 to be coupledto exhaust gas after treatment device 70.

After treatment device 70 can include multiple catalyst bricks, in oneexample. In another example, multiple emission control devices, eachwith multiple bricks, can be used. After treatment device 70 may be athree-way type catalyst in one example. In other examples, the aftertreatment device may be a particulate filter or an oxidation catalyst.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106 (e.g., non-transitory memory), random access memory 108, keepalive memory 110, and a conventional data bus. Controller 12 is shownreceiving various signals from sensors coupled to engine 10, in additionto those signals previously discussed, including: engine coolanttemperature (ECT) from temperature sensor 112 coupled to cooling sleeve114; a position sensor 134 coupled to an propulsion pedal 130 forsensing force applied by human driver 132; a position sensor 154 coupledto brake pedal 150 for sensing force applied by human driver 132, ameasurement of engine manifold pressure (MAP) from pressure sensor 122coupled to intake manifold 44; an engine position sensor from a Halleffect sensor 118 sensing crankshaft 40 position; a measurement of airmass entering the engine from sensor 120; and a measurement of throttleposition from sensor 68. Barometric pressure may also be sensed (sensornot shown) for processing by controller 12. In a preferred aspect of thepresent description, engine position sensor 118 produces a predeterminednumber of equally spaced pulses every revolution of the crankshaft fromwhich engine speed (RPM) can be determined.

Controller 12 may also receive input from human/machine interface 11. Arequest to start the engine or vehicle may be generated via a human andinput to the human/machine interface 11. The human/machine interface maybe a touch screen display, pushbutton, key switch or other known device.Controller 12 may also automatically start engine 10 in response tovehicle and engine operating conditions. Automatic engine starting mayinclude starting engine 10 without input from human 132 to a device thatis dedicated to receive input from human 132 for the sole purpose ofstarting and/or stopping rotation of engine 10 (e.g., a key switch orpushbutton). For example, engine 10 may be automatically stopped inresponse to driver demand torque being less than a threshold and vehiclespeed being less than a threshold.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into combustion chamber 30 via intake manifold 44, and piston36 moves to the bottom of the cylinder so as to increase the volumewithin combustion chamber 30. The position at which piston 36 is nearthe bottom of the cylinder and at the end of its stroke (e.g. whencombustion chamber 30 is at its largest volume) is typically referred toby those of skill in the art as bottom dead center (BDC).

During the compression stroke, intake valve 52 and exhaust valve 54 areclosed. Piston 36 moves toward the cylinder head so as to compress theair within combustion chamber 30. The point at which piston 36 is at theend of its stroke and closest to the cylinder head (e.g. when combustionchamber 30 is at its smallest volume) is typically referred to by thoseof skill in the art as top dead center (TDC). In a process hereinafterreferred to as injection, fuel is introduced into the combustionchamber. In a process hereinafter referred to as ignition, the injectedfuel is ignited by known ignition means such as spark plug 92, resultingin combustion.

During the expansion stroke, the expanding gases push piston 36 back toBDC. Crankshaft 40 converts piston movement into a rotational torque ofthe rotary shaft. Finally, during the exhaust stroke, the exhaust valve54 opens to release the combusted air-fuel mixture to exhaust manifold48 and the piston returns to TDC. Note that the above is shown merely asan example, and that intake and exhaust valve opening and/or closingtimings may vary, such as to provide positive or negative valve overlap,late intake valve closing, or various other examples.

Referring now to FIG. 2, an example fuel system 275 is shown. The fuelsystem of FIG. 2 may supply fuel to engine 10 shown in detail in FIG. 1.Fuel system 275 includes evaporative emission system 270. The system ofFIG. 2 may be operated according to the method of FIGS. 3A-3C. Fuelsystem components and fluidic conduits are shown as solid lines andelectrical connections are shown as dashed lines. The conduitsrepresented by solid lines provide fluidic communication between deviceslinked by the conduits. Further, the conduits are coupled to the devicesfrom which and to which they lead.

Evaporative emissions system 270 includes a fuel vapor storage canister202 for storing fuel vapors. Evaporative emissions system 270 alsoincludes carbon 203 for storing and releasing fuel vapors. Fuel vaporstorage canister 202 is shown including atmospheric vent line 205 alongwhich normally closed canister vent valve (CVV) 213 is placed toselectively allow air to flow into and out of fuel vapor storagecanister 202. Fuel vapors may be supplied to fuel vapor storage canister202 via conduit 208 and normally open fuel vapor blocking valve (VBV)219. Fuel vapors may be purged via canister purge valve (CPV) 204 whichallows fluidic communication between fuel vapor storage canister 202 andengine intake manifold 44 or intake 42 via conduit 207.

Engine 10 includes a fuel rail 220 that supplies fuel to direct fuelinjector 66. Fuel vapors may be inducted into intake manifold 44 orintake 42 when intake manifold pressure is below atmospheric pressure.Fuel 231 is supplied from fuel tank 230 by fuel pump 252 to fuel rail220. Pressure in fuel tank 232 may be measured via fuel tank pressuretransducer (FTPT) 241 and relayed to controller 12. Controller 12 mayreceive inputs from the sensors described in FIG. 1 as well as sensor241. Controller 12 also activates and deactivates CPV 204, CVV 213, VBV219, and pump 252 in response to fuel system and engine operatingconditions.

In one example, the system of FIG. 2 operates according to the method ofFIGS. 3A-3C via executable instructions stored in non-transitory memoryof controller 12. While engine 10 is operating, fuel vapors from fueltank 230 may be stored in fuel vapor storage canister 202 in response totemperatures in fuel tank 230 increasing.

Fuel vapors from fuel tank 230 may push air out of normally open CVV 213when temperature and/or pressure in fuel tank 230 is increasing. Ifengine 10 is operating while vapors are being directed to fuel vaporstorage canister 202, CPV 204 may be opened so that fuel vapors aredrawn into and combusted in engine 10. If engine 10 is not operating orif CPV 204 is closed, fuel vapor may flow into fuel vapor storagecanister 202 if temperature and/or pressure in fuel tank 230 increasessuch that fuel vapors flow to and are stored in fuel vapor storagecanister 202.

On the other hand, if engine 10 is not operating or if CPV 204 is closedwhile temperature and/or pressure in fuel tank 230 is decreasing, fuelvapors from fuel vapor canister 202 may condense in fuel tanks 230 whenVBV 219 is open. VBV 219 may be a normally open valve that is closedwhen CPV is open to improve vacuum formation in canister 202, therebyimproving evacuation of fuel vapors from fuel vapor storage canister202. Thus, the fuel system shown in FIG. 2 provides a way of decreasinga volume of the fuel vapor emissions system that is purged so that fuelvapor canister purging may be improved.

Thus, the system of FIGS. 1 and 2 provides for a system, comprising: anengine including a plurality of cylinders having a plurality of fuelinjectors and an after treatment device; a canister including storedfuel vapors; a purge control valve in fluidic communication with thecanister; and a controller including executable instructions stored innon-transitory memory that cause the controller to adjust a position ofthe purge control valve in response to an estimate of a temperature ofthe after treatment device while fuel vapors flow from the purge controlvalve to the after treatment device and while the engine is operating ina fuel cut-out mode where fuel is not injected to engine cylinders viathe plurality of fuel injectors. The system includes wherein the fuelvapors flow from the purge control valve to the after treatment devicevia at least partially opening the purge control valve. The systemincludes where the estimate of the temperature of the after treatmentdevice is based on a fuel cloud. The system includes where opening thepurge control valve supplies fuel to the fuel cloud. The system includeswhere adjusting the position of the purge control valve includes closingthe purge control valve in response to the estimate of the temperaturebeing greater than a threshold temperature. The system further comprisesadditional instructions to estimate an amount of fuel being combustedvia the after treatment device. The system further comprises additionalinstructions to adjust an exotherm temperature in response to exiting afuel vapor canister purge mode.

Referring now to FIGS. 3A-3C, a flow chart of a method for estimating atemperature of an after treatment device and operating an engine isshown. The method of FIGS. 3A-3C may be incorporated into and maycooperate with the system of FIGS. 1 and 2. Further, at least portionsof the method of FIGS. 3A-3C may be incorporated as executableinstructions stored in non-transitory memory while other portions of themethod may be performed via a controller transforming operating statesof devices and actuators in the physical world.

At 302, method 300 determines operation conditions. Operating conditionsmay include but are not limited to ambient temperature, enginetemperature, engine speed, barometric pressure, engine air flow, engineload, spark timing, and driver demand torque. Method 300 proceeds to304.

At 304, method 300 estimates exhaust gas temperature and flow rate. Inone example, method 300 may determine exhaust gas temperature and flowrate via the following equations:

Exh_Engine_(out)=ƒ1(N,AM,Spk_del,EGR,ECT,LAM)

Exh_flow=AM+FM

where Exh_Engine_(out) is the estimated exhaust gas temperature leavingthe exhaust manifold (flange), f1 is a function that returns theestimated exhaust gas temperature at the flange, N is engine speed, AMis air mass flow through the engine, Spk_del is spark timing differencefrom minimum spark for best engine torque, EGR is the exhaust gasrecirculation amount, ECT is engine temperature, and LAM is the engineair-fuel ratio divided by the stoichiometric air-fuel ratio, Exh_flow isthe exhaust flow rate, FM is the fuel mass flow rate. Method 300proceeds to 306.

At 306, method 300 estimates an exhaust after treatment device inlettemperature. In one example, method 300 determines exhaust temperatureat the inlet of the exhaust after treatment device via the followingequation:

Exh_ATDevice_(inlet)=Exh_temp−Exh_Loss

where Exh_ATDevice_(inlet) is exhaust temperature at the exhaust aftertreatment device inlet, Exh_temp is exhaust temperature at the exhaustflange, and Exh_Loss is a temperature drop. Exh_Loss may be determinedas a function of engine air flow rate and a table of empiricallydetermined values generated while driving a vehicle and measuringexhaust temperature drop. Method 300 determines the exhaust aftertreatment device inlet temperature and proceeds to 308.

At 308, method 300 judges if the engine is operating with astoichiometric air-fuel ratio and an exhaust after treatment temperatureis greater than a threshold temperature. Method 300 may determine if theengine is operating with a stoichiometric air-fuel ratio based on outputof an exhaust gas oxygen sensor. Method may judge if the exhaust aftertreatment temperature is greater than at threshold based on a presentexhaust after treatment temperature estimate. If method 300 judges thatthe engine is operating with a stoichiometric air-fuel ratio and withexhaust after treatment temperature greater than a thresholdtemperature, the answer is yes and method 300 proceeds to 320.Otherwise, the answer is no and method 300 proceeds to 310.

At 320, method 300 estimates a after treatment device exothermtemperature based on stoichiometric operating conditions. Method 300estimates an after treatment device exotherm temperature according tothe following equation:

ATExotherm_(stoich)=ƒ2(AM)

where ATExotherm_(stoich) is a variable that represents the aftertreatment device exotherm temperature during stoichiometric engineoperating conditions, f2 is a function that returns empiricallydetermined after treatment device exotherm valves as a function ofengine air mass (AM) for when the engine is operating with astoichiometric air-fuel ratio. Values in function f2 may be determinedvia driving a vehicle while the vehicle's engine operates with astoichiometric air-fuel ratio and recording after treatment devicetemperature as a function of engine air mass. Method 300 proceeds to 322after determining the after treatment device exotherm temperature.

At 322, method 300 estimates the after treatment device temperature.Method 300 may determine a feed-forward steady state after treatmentdevice temperature according to the following equation:

Exh_ATDevice_(SteadyState)=Exh_ATDevice_(inlet)+ATExotherm_(stoich)

where Exh_ATDevice_(SteadyState) is the steady state after treatmentdevice temperature, ATExotherm_(stoich) is the after treatment deviceexotherm for stoichiometric engine operation, and Exh_ATDevice_(inlet)is the temperature at the after treatment device inlet. The final aftertreatment device temperature may be determined via the followingequation:

Exh_ATDevice_(Midbed)=(1−FK)Exh_ATDevice_(inlet)+FK(Exh_ATDevice_(SteadyState))

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, FK is a low pass filter constant, andExh_ATDevice_(SteadyState) is the steady state after treatment devicetemperature. Method 300 proceeds to exit.

In some examples, actuators of the engine may be adjusted in response tothe after treatment device mid-bed temperature. For example, if mid-bedtemperature exceeds a threshold temperature, then method 300 may richenthe engine air-fuel ratio to reduce the exotherm. In addition, method300 may adjust spark timing to reduce the exotherm. For example, method300 may advance spark timing to reduce exhaust gas temperatures in aneffort to reduce the exotherm.

At 310, method 300 judges if the engine is operating with fuel vaporcanister purge activated during fuel cut-out conditions. Fuel vaporcanister purge may be activate via opening the canister purge valve toallow fuel vapors to exit the fuel vapor storage canister and enter theengine intake manifold. The fuel vapors may be pumped from the intakemanifold to an after treatment device via the engine as the enginerotates. Canister purge may be activated in response to an estimate ofan amount of fuel vapors that are stored in the fuel vapor storagecanister (e.g., 203 if FIG. 2). The engine may be operated in a fuelcut-out mode in response to vehicle speed and driver demand torque. Inparticular, when vehicle speed is greater than a threshold speed anddriver demand torque is less than a threshold torque, the engine mayenter fuel cut-out mode where fuel is not injected into the engine viafuel injectors to conserve fuel. In addition, the engine continues torotate without being fueled via the fuel injectors while in fuel cut-outmode. If method 300 judges that engine is operating in fuel cut-out modewith canister purge activated, the answer is yes and method 300 proceedsto 330. Otherwise, method 300 proceeds to 312.

At 330, method 300 estimates an after treatment device exotherm for whenthe engine is operating in a fuel cut-out mode with purge activated.Method 300 may determine the after treatment device exotherm accordingto an estimate of purge fuel flowing through the engine and to the aftertreatment device. In one example, method 300 may determine the purgefuel flow according to the following equation:

Flow_(Purge)=HC_con*ƒ3(dty,MAP,T_HC,BP)

where Flow_(Purge) is the fuel mass flow rate, HC_con is a hydrocarbonconcentration in purge vapor flowing to the engine, which may bedetermined via a HC sensor, f3 is a function that determines a mass flowrate of purge fuel vapors, dty is a purge valve duty cycle, MAP isintake manifold pressure, BP is barometric pressure, and T_HC is thetemperature of fuel vapors. For purge vapor, the mass of fuel enteringand leaving the fuel cloud are identical, everything that enters will becombusted causing an exotherm. A rolling average purge flow rate iscalculated to avoid rapid changes in exotherm.

Flow_(PurgeAve)=ΣFlow_(Purge)/ΣTime

ATExotherm_(Purge)=ƒ3(AM)*Flow_(PurgeAve)

where ATExotherm_(Purge) is the after treatment device exotherm due topurge when in fuel cut and β3 is a function that returns empiricallydetermined after treatment device exotherm per unit of purge flow as afunction of engine air mass (AM) for when purge is introduced in fuelcut conditions.

At 332, method 300 estimates the after treatment device temperatureincluding the exotherm according to purge conditions. Method 300 maydetermine a steady state after treatment device temperature according tothe following equation:

Exh_ATDevice_(Midbed)=Exh_ATDevice_(Midbed)+ATExotherm_(Purge)

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, ATExotherm_(Purge) is the after treatment device exothermdue to purge when in fuel cut, Method 300 proceeds to exit.

In some examples, actuators of the engine may be adjusted in response tothe after treatment device mid-bed temperature. For example, if mid-bedtemperature exceeds a threshold temperature, then method 300 may reducea duty cycle or valve opening amount of the canister purge valve toregulate the exotherm. In some examples, method 300 may also adjust airflow through the throttle to reduce the exotherm.

At 312, method 300 judges if the engine has recently exited fuel vaporcanister purge (e.g., if the engine has exited fuel vapor canister purgewithin a predetermined amount of time). Method 300 may judge that theengine has exited fuel vapor canister purge if the canister purge valvehas closed. If method 300 judges that the engine has recently exited thefuel vapor canister purge while operating in fuel cut-out mode, method300 proceeds to 340.

At 340, method 300 adjusts the after treatment device exotherm accordingto fuel vapor canister purge exit conditions as described in FIG. 3C.Method 300 proceeds to exit.

In some examples, actuators of the engine may be adjusted at 340 inresponse to the after treatment device mid-bed temperature. For example,if mid-bed temperature exceeds a threshold temperature, then method 300may reduce a fuel injection timing to reduce fuel delivered toreactivate the after treatment device.

At 314, method 300 judges if the engine has recently exited all cylinderfuel cut-out mode and started reactivating one or more after treatmentdevices. All cylinder cut-out includes ceasing to supply fuel to allengine cylinders (e.g., fuel flow is ceased to eight cylinders of anengine that includes an actual total of eight cylinders) while theengine continues to rotate via energy provided by the vehicle's wheels.Method 300 may judge that the engine has exited all cylinder cut-outmode when the engine begins operating all of the engine's fuel injectorsafter all of the engine's fuel injectors have ceased injecting fuel. Theafter treatment device may have become saturated with oxygen while theengine operated in fuel cut-out mode and the engine pumped fresh air tothe after treatment device as the engine is rotated. Once the aftertreatment device becomes saturated with oxygen, it may be less efficientat reducing NOx. However, the after treatment device may be reactivatedsuch that it begins to reduce NOx efficiently if the engine beginscombusting a rich air-fuel mixture or via injecting fuel such thathydrocarbons that have not combusted reach the after treatment device.If method 300 judges that the engine has recently exited all cylinderfuel cut-out mode and started to reactivate one or more after treatmentdevices, the answer is yes and method 300 proceeds to 317. Otherwise,the answer is no and method 300 proceeds to 315.

At 315, method 300 estimates an after treatment device exothermtemperature based on engine Lambda operating conditions. Method 300estimates an after treatment device exotherm temperature according tothe following equation:

ATExoMult_(Lambda)=ƒ4(AM,Lambda)

where ATExoMult_(Lambda) is a variable that represents the aftertreatment device exotherm temperature multiplier during other thanstoichiometric engine operating conditions, f4 is a function thatreturns empirically determined after treatment device exotherm valves asa function of engine air mass (AM) and Lambda (e.g., engine air-fuelratio/stoichiometric air-fuel ratio) for when the engine is notoperating with a stoichiometric air-fuel ratio. Values in function f4may be determined via driving a vehicle while the vehicle's engineoperates with other than a stoichiometric air-fuel ratio and recordingafter treatment device temperature as a function of engine air mass andLambda. Method 300 proceeds to 316 after determining the after treatmentdevice exotherm temperature.

At 316, method 300 estimates the after treatment device temperature.Method 300 may determine a steady state after treatment devicetemperature according to the following equation:

Exh_ATDevice_(SteadyState)=Exh_ATDevice_(inlet)+(ATExotherm_(stoich)*ATExoMult_(Lambda))

where Exh_ATDevice_(SteadyState) is the steady state after treatmentdevice temperature, ATExoMult_(Lambda) is the after treatment deviceexotherm multiplier for other than stoichiometric engine operation, andExh_ATDevice_(inlet) is the temperature at the after treatment deviceinlet. The final after treatment device temperature may be determinedvia the following equation:

Exh_ATDevice_(Midbed)=(1−FK)Exh_ATDevice_(Midbed)+FK(Exh_ATDevice_(SteadyState))

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, FK is a low pass filter constant, andExh_ATDevice_(SteadyState) is the steady state after treatment devicetemperature. Method 300 proceeds to exit.

At 317, method 300 estimates an after treatment device exotherm based onfuel supplied to the exhaust gases that is applied to reactivate theafter treatment device. In one example, method 300 may determine theafter treatment device reactivation fuel flow according to the followingequation:

mf_acum=mf_acum_(previous) +mf_react_(added) +mf_react_(exo)

where mf_acum is the fuel mass supplied to reactivate the exhaust aftertreatment device, mf_acum_(previous) is the amount of unburned fuelremaining in the exhaust from the last calculation event, andmf_react_(added) is the amount of fuel added for reactivation duringthis calculation event, mf_react_(exo) is the amount of fuel expected tocombust and create exotherm during this calculation event. The mass offuel leaving a fuel cloud in the exhaust system may be determined viathe following equation:

mf_react_(exo) =mf_acum*mf_exo_mul(AM)

where mf_react_(exo) is the fuel leaving the fuel cloud within theexhaust system, mf_acum is the total fuel amount in the fuel cloudwithin the exhaust system, mf_exo_mul(AM) is the fraction of fuelleaving the fuel cloud within the exhaust systems a function of air massflow rate through the engine. In one example, the variablemf_exo_mul(AM) may be stored in memory as a 2×4 matrix and values in thematrix may be empirically determined or modeled. The fraction of fuelleaving the fuel cloud in the exhaust system and being combusted in theexhaust after treatment device may be determined via the followingequation:

mf_comb=mf_react_(exo)−mf_temp_mul(Exh_ATDevice_(Midbed))·mf_O2_mul(O2conc)

where mf_comb is the mass of fuel leaving the fuel cloud in the exhaustsystem and being combusted in the exhaust after treatment device,mf_react_(exo) is the mass of fuel that is leaving the fuel cloud in theexhaust system, mf_temp_mul(Exh_ATDevice_(Midbed)) is the fraction offuel combusted as a function of after treatment device mid-bedtemperature Exh_ATDevice_(Midbed), mf_O2_mul(O2conc) return a multiplierto the fuel mass as a function of the amount of oxygen stored in theexhaust after treatment device during fuel cut-out (O2conc). Theparameter mf_temp_mul(Exh_ATDevice_(Midbed)) may be determinedempirically by comparing the exotherm generated at consistent aftertreatment oxygen saturation with varying after treatment devicetemperatures. The parameter mf_O2_mul(O2conc) may be determinedempirically by comparing the exotherm generated at consistent aftertreatment device temperatures with varying oxygen saturation. Theparameter O2_(stored) may be calculated by determining the oxygen flowrate due to partial or non-firing cylinders until the after treatmentdevice is saturated. The after treatment device exotherm for when theengine is operating in a fuel cut-out mode with purge activated may bedetermined via the following equation:

ATExotherm_(React) =mf_exo_mul*mf_comb

where ATExotherm_(React) is the after treatment device exotherm forafter treatment device reactivation for the present iteration,mf_exo_mul is the expected after treatment device exotherm temperaturerise per unit of fuel available for combustion and mf_comb is aspreviously described. Method 300 also enters after treatmentreactivation mode via increasing fuel injected and fuel delivered to theafter treatment device. Fuel for reactivating the after treatment devicemay be injected during an intake or exhaust stroke of the engine. Method300 proceeds to 318.

At 318, method 300 estimates the after treatment device temperatureincluding the exotherm according to after treatment reactivationconditions. The final after treatment device temperature may bedetermined via the following equation:

Exh_ATDevice_(Midbed)=Exh_ATDevice_(Midbed)+ATExotherm_(React)

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, ATExotherm_(React) is the exotherm that can be attributedto reactivation of the after treatment device. Method 300 proceeds toexit.

Referring now to FIG. 3C, a method for adjusting the exhaust aftertreatment device exotherm after exiting fuel vapor canister purge duringfuel cut-out mode is shown. The method of FIG. 3C may operate inconjunction with the method of FIGS. 3A and 3B and the system shown inFIGS. 1 and 2.

At 350, method 300 judges if fuel vapor canister purge mode has beenexited based on or due to closing of the canister purge valve. Thecanister purge valve may be closed when it is determined that less thana threshold amount of fuel vapors are being purged from the fuel vaporstorage canister. If method 300 judges that the fuel vapor canisterpurge mode has been exited based on closing of the canister purge valve,the answer is yes and method 300 proceeds to 351. Otherwise, method 300proceeds to 352.

At 351, method 300 reduces the exhaust after treatment device exothermbased on exiting the fuel vapor canister purge mode in response to thepurge valve closing while remaining in fuel cutoff. In one example,method 300 may reduce the exhaust after treatment device exotherm at afirst predetermined rate. For example, the variable ATExotherm_(Purge)may be revised each time method 300 is executed as prescribed in thefollowing equation:

ATExotherm_(Purge)=ƒ3(AM)*(Flow_(PurgeComb)*decay_rate)

where ATExotherm_(Purge) is the present value of the after treatmentdevice exotherm for operating the fuel cut-out mode with purgeactivated, ƒ3 is a function that returns empirically determined aftertreatment device exotherm per unit of purge flow as a function of engineair mass (AM) for when purge is introduced in fuel cut conditions (asoutlined previously), Flow_(PurgeComb) is the purge remaining in theexhaust flow and decay_rate is the desired decay rate of remaining purgein the exhaust stream, Flow_(PurgeComb) until all remaining purge hasbeen combusted.

Method 300 also revises the exhaust after treatment device temperaturebased on the revised value of Exh_ATDevice_(Midbed). In particular,method 300 determines the steady state after treatment devicetemperature according to the following equation:

Exh_ATDevice_(Midbed)=Exh_ATDevice_(Midbed)+ATExotherm_(Purge)

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, ATExotherm_(Purge), is the after treatment device exothermdue to purge when in fuel cut. Method 300 proceeds to exit.

At 352, method 300 judges if fuel vapor canister purge mode has beenexited based on activating combustion in engine cylinders. The canisterpurge mode may be exited in response to an increase in driver demandtorque that causes cylinders to be reactivated. If method 300 judgesthat the fuel vapor canister purge mode has been exited based onactivating combustion in engine cylinders, the answer is yes and method300 proceeds to 353. Otherwise, method 300 proceeds to 354.

At 353, method 300 reduces the exhaust after treatment device exothermbased on exiting the fuel vapor canister purge mode in response tocylinders being reactivated. In one example, method 300 may reduce theremaining combustible purge due to the cylinder re-enablement andreduction in exhaust oxygen concentration. For example,Flow_(PurgeComb), may be revised one time as outlined in the followingequation:

Flow_(PurgeComb)=(Flow_(PurgeComb)*Offset_(Comb))

where Flow_(PurgeComb), is the purge remaining in the exhaust flow andOffset_(Comb) is offset multiplier to account for the decrease in purgecombustion due to cylinder reactivation and reduction in exhaust oxygenconcentration. Further, method 300 reduces the exhaust after treatmentdevice exotherm based on exiting the fuel vapor canister purge mode inresponse to cylinder re-enablement. For example, the variableATExotherm_(Purge) may be revised each time method 300 is executed asprescribed in the following equation:

ATExotherm_(Purge)=ƒ3(AM)*(Flow_(PurgeComb)*decay_rate*decay_mult)

where ATExotherm_(Purge) is the present value of the after treatmentdevice exotherm for operating the fuel cut-out mode with purgeactivated, ƒ3 is a function that returns empirically determined aftertreatment device exotherm per unit of purge flow as a function of engineair mass (AM) for when purge is introduced in fuel cut conditions (asoutlined previously), Flow_(PurgeComb) is the purge remaining in theexhaust flow, decay_rate is the desired decay rate of remaining purge inthe exhaust stream and decay_mult is a decay rate multiplier to increasethe decay rate due to active combustion.

Method 300 also revises the exhaust after treatment device temperaturebased on the revised value of Exh_ATDevice_(Midbed) In particular,method 300 determines the steady state after treatment devicetemperature according to the following equation:

Exh_ATDevice_(Midbed)=Exh_ATDevice_(Midbed)+ATExotherm_(Purge)

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, ATExotherm_(Purge) is the after treatment device exothermdue to purge when in fuel cut. Method 300 proceeds to exit.

At 354, method 300 judges if fuel vapor canister purge mode has beenexited based on a reduction in hydrocarbon flow from the fuel vaporstorage canister to the engine and exhaust after treatment device. Thehydrocarbon flow rate may be reduced as the fuel vapor storage canisteris purged of fuel vapors. If method 300 judges that the fuel vaporcanister purge mode has been exited based on a reduction in hydrocarbonflow, the answer is yes and method 300 proceeds to 355. Otherwise,method 300 proceeds to 356.

At 355, method 300 reduces the exhaust after treatment device exothermto zero because any remaining purge mass in the exhaust is not largeenough to create a exotherm in the after treatment device.

Method 300 also revises the exhaust after treatment device temperaturebased on the revised value of Exh_ATDevice_(Midbed). In particular,method 300 determines the after treatment device temperature accordingto the following equation:

Exh_ATDevice_(Midbed)=Exh_ATDevice_(Midbed)+ATExotherm_(Purge)

where Exh_ATDevice_(Midbed) is the after treatment device mid-bedtemperature, ATExotherm_(Purge), is zero. Method 300 proceeds to exit.

Thus, the method of FIGS. 3A-3C provides for an engine operating method,comprising: operating an engine in a fuel cut-out mode wherein theengine rotates without injecting fuel to the engine via fuel injectors;delivering fuel to the engine via a fuel vapor canister while operatingthe engine in the fuel cut-out mode; and estimating a temperature of anexhaust after treatment device via a controller, the controllerestimating the temperature of the exhaust after treatment device basedon combusting fuel supplied from the fuel vapor canister in the exhaustafter treatment device while operating the engine in the fuel cut-outmode. The method further comprises adjusting an actuator in response tothe estimated temperature. The method includes where the actuator is apurge control valve. The method further comprises decreasing an openingamount of the purge control valve in response to the estimate of thetemperature of the exhaust after treatment device exceeding a thresholdtemperature. The method includes where estimating the temperature of theexhaust after treatment device includes estimating an amount of fuelcombusting after leaving a fuel cloud. The method includes where thefuel cloud includes fuel supplied from the fuel vapor canister. Themethod further comprises estimating an amount of fuel stored in the fuelcloud.

The method of FIGS. 3A-3C also provides for an engine operating method,comprising: operating an engine in a fuel cut-out mode via a controllerwherein the engine rotates without injecting fuel to the engine via fuelinjectors; delivering fuel to the engine via a fuel vapor canister whileoperating the engine in the fuel cut-out mode; estimating an amount offuel being delivered to the engine via the fuel vapor canister;estimating an amount of fuel stored in a fuel cloud, the fuel cloudcontaining fuel from the fuel vapor canister; estimating an amount offuel exiting the fuel cloud and combusting in an exhaust after treatmentdevice; and estimating a temperature of the exhaust after treatmentdevice via the controller, the controller estimating the temperature ofthe exhaust after treatment device based on the estimate of fuel amountof fuel exiting the fuel cloud. The method further comprises adjustingan actuator in response to the estimated temperature. The methodincludes where the actuator is a purge control valve. The methodincludes where the actuator is a throttle. The method further comprisesestimating an amount of fuel stored in the fuel cloud. The methodfurther comprises closing the purge valve in response to the estimate ofthe amount of fuel being delivered to the engine via the fuel vaporcanister.

Referring now to FIG. 4, an example fuel vapor storage canister purgingevent during an engine fuel cut-out mode is shown. The sequence of FIG.4 may be generated via the system of FIGS. 1 and 2 in cooperation withthe method of FIGS. 3A-3C. Vertical lines at times t0-t3 represent timesof interest during the sequence. The plots in FIG. 4 are time alignedand occur at the same time.

The first plot from the top of FIG. 4 is a plot of engine operatingstate versus time. The vertical axis represents engine operating stateand the engine is requested to be on or run (e.g., rotate and combustfuel and air) when trace 402 is at a higher level near the vertical axisarrow. The engine is requested to be in or is in fuel cut-out mode(e.g., the engine is rotating without delivering fuel to the engine'scylinders) when trace 402 is at the level cut indicated along thevertical axis. The engine is requested to stop or is stopped (e.g., notrotating and combusting air and fuel) when trace 402 is at a lower levelnear the horizontal axis. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 402 represents the engine operating state.

The second plot from the top of FIG. 4 is a plot of propulsion pedalposition versus time. The vertical axis represents propulsion pedalposition and the propulsion pedal is applied further in the direction ofthe vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 404 represents the propulsion pedal position.

The third plot from the top of FIG. 4 is a plot of an estimated aftertreatment device temperature versus time. The vertical axis representsthe estimated after treatment device temperature and estimated aftertreatment device temperature increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the plot to the right side of the plot. Trace 406represents the after treatment device temperature. Horizontal line 450represents an upper threshold or limit not to be exceeded and horizontalline 452 represents an after treatment light off temperature.

The fourth plot from the top of FIG. 4 is a plot of engine exhaust gastemperature versus time. The vertical axis represents engine exhaust gastemperature at the exhaust flange upstream of the engine exhaust aftertreatment device. The horizontal axis represents time and time increasesfrom the left side of the plot to the right side of the plot. Trace 408represents the engine exhaust gas temperature.

The fifth plot from the top of FIG. 4 is a plot of a fuel vapor canisterpurge state versus time. The vertical axis represents fuel vapor purgestate and fuel vapor purge is activated (e.g., flowing fuel vapors fromthe fuel vapor canister to the engine) when trace 410 is at a higherlevel near the vertical axis arrow. Fuel vapor canister purge is notactivated when trace 410 is at a lower level near the horizontal axis.The horizontal axis represents time and time increases from the leftside of the plot to the right side of the plot. Trace 410 represents thefuel vapor canister purge state.

The sixth plot from the top of FIG. 4 is a plot of fuel vapor purge flowrate versus time. The vertical axis represents fuel vapor purge flowrate and the fuel vapor flow rate increases in the direction of thevertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 412 represents the fuel vapor purge flow rate.

At time t0, the engine state is running (e.g., rotating and combustingfuel). The propulsion pedal is applied and the estimated after treatmentdevice temperature is above level 452 and below level 450. The engineexhaust temperature is at a higher level and fuel vapor canister purgeis not activated. The purge flow rate is zero.

At time t1, the propulsion pedal is fully released while the engine isrunning. The catalyst temperature and other variables are at theirprevious levels. Shortly after time t1, the engine enters fuel cut-outmode and the estimated after treatment device temperature begins to coolas the engine pumps a small amount of air to the after treatment device.Fuel vapor canister purge begins shortly after the engine enters fuelcut-out mode and the fuel vapor canister purge flow rate is increased.The estimated after treatment device temperature begins increasing asfuel vapors are oxidized within the engine after treatment device. Thepurge flow rate is reduced via partially closing the purge valve (notshown) as the estimated after treatment device temperature approachesthreshold 450. Thus, the estimated after treatment device temperatureand the actual after treatment device temperature may be regulated viaadjusting the position or duty cycle of the purge valve.

At time t2, the fuel vapor canister purge mode is exited. The fuel vaporcanister purge mode may be exited based on duration of purging, areduction in purge vapors, or other operating conditions. The purge flowrate is reduced to zero via closing the purge valve and the engineremains in fuel cut-out mode. The propulsion pedal is not applied andthe engine exhaust temperature is low. The estimated after treatmentdevice temperature begins to be reduced.

At time t3, the propulsion pedal is applied and the engine isreactivated in response to an increase in driver demand torque asdetermined from propulsion pedal position. The estimated after treatmentdevice temperature begins to increase and the engine exhaust temperatureincreases. The fuel canister purge remains deactivated and the purgeflow rate remains at zero.

In this way, temperature of an after treatment device may be estimatedand controlled during engine fuel cut-out mode. In particular, the aftertreatment device temperature may be regulated via adjusting a positionof a purge valve.

Referring now to FIG. 5, an example reactivation event of an engineexhaust gas after treatment device after exiting an engine fuel cut-outmode is shown. The sequence of FIG. 5 may be generated via the system ofFIGS. 1 and 2 in cooperation with the method of FIGS. 3A-3C. Verticallines at times t10-t13 represent times of interest during the sequence.The plots in FIG. 4 are time aligned and occur at the same time.

The first plot from the top of FIG. 5 is a plot of engine operatingstate versus time. The vertical axis represents engine operating stateand the engine is requested to be on or run (e.g., rotate and combustfuel and air) when trace 502 is at a higher level near the vertical axisarrow. The engine is requested to be in or is in fuel cut-out mode(e.g., the engine is rotating without delivering fuel to the engine'scylinders) when trace 502 is at the level cut indicated along thevertical axis. The engine is requested to stop or is stopped (e.g., notrotating and combusting air and fuel) when trace 502 is at a lower levelnear the horizontal axis. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 502 represents the engine operating state.

The second plot from the top of FIG. 5 is a plot of propulsion pedalposition versus time. The vertical axis represents propulsion pedalposition and the propulsion pedal is applied further in the direction ofthe vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 504 represents the propulsion pedal position.

The third plot from the top of FIG. 5 is a plot of an estimated aftertreatment device temperature versus time. The vertical axis representsthe estimated after treatment device temperature and estimated aftertreatment device temperature increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the plot to the right side of the plot. Trace 506represents the after treatment device temperature. Horizontal line 550represents an upper threshold or limit not to be exceeded and horizontalline 552 represents an after treatment light off temperature.

The fourth plot from the top of FIG. 5 is a plot of engine exhaust gastemperature versus time. The vertical axis represents engine exhaust gastemperature at the exhaust flange upstream of the engine exhaust aftertreatment device. The horizontal axis represents time and time increasesfrom the left side of the plot to the right side of the plot. Trace 508represents the engine exhaust gas temperature.

The fifth plot from the top of FIG. 5 is a plot of an engine exhaust gasafter treatment device reactivation state versus time. The vertical axisrepresents the reactivation state of the engine exhaust gas aftertreatment device. The engine exhaust gas after treatment device is beingreactivated (e.g., via supplying hydrocarbons to the after treatmentdevice) when trace 510 is at a higher level near the vertical axisarrow. The engine exhaust gas after treatment device is not beingreactivated when trace 510 is at a lower level near the horizontal axis.Trace 510 represents the engine exhaust gas after treatment devicereactivation state,

The sixth plot from the top of FIG. 5 is a plot of reactivation fuelflow rate versus time. The vertical axis represents reactivation fuelflow rate and the reactivation fuel flow rate increases in the directionof the vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Trace 512 represents the reactivation fuel flow rate.

At time t10, the engine state is running (e.g., rotating and combustingfuel). The propulsion pedal is applied and the estimated after treatmentdevice temperature is above level 552 and below level 550. The engineexhaust temperature is at a higher level and the engine exhaust gasafter treatment device is not being reactivated. The reactivation fuelflow rate is zero.

At time t11, the propulsion pedal is fully released while the engine isrunning. The catalyst temperature and other variables are at theirprevious levels. Shortly after time t11, the engine enters fuel cut-outmode and the estimated after treatment device temperature begins to coolas the engine pumps a small amount of air to the after treatment device.The engine exhaust temperature begins to cool and the engine exhaust gasafter treatment device is not be reactivated. The reactivation fuel flowrate is zero.

At time t12, the engine exits fuel cut-out mode in response to driverdemand increasing as the position of the propulsion pedal increases. Theengine exhaust gas temperature also increases as engine cylinders arereactivated (not shown). Reactivation of the engine exhaust gas aftertreatment device begins and reactivation fuel flow to the engine exhaustgas after treatment device increases. The estimated exhaust gas aftertreatment device temperature is increased due to activating cylindersand supplying fuel to the engine exhaust gas after treatment device.

Between time t12 and time t13, the amount of reactivation fuel flow isincreased and then it is decreased in response to the estimated exhaustafter treatment device temperature approaching threshold 550. The amountof reactivation fuel flow may be adjusted via adjusting fuel injectiontiming. Thus, by adjusting fuel injection timing, temperature of theexhaust after treatment device may be regulated.

At time t13, the catalyst reactivation ceases and the reactivation fuelflow rate is reduced to zero. Catalyst reactivation may cease inresponse to delivering a desired amount of fuel to the exhaust aftertreatment device or in response to output of a NOx sensor.

In this way, temperature of an after treatment device may be estimatedand controlled during reactivation of an engine exhaust after treatmentdevice. In particular, the after treatment device temperature may beregulated via adjusting a timing of fuel injection.

Referring now to FIG. 6, a graphic depiction of a fuel cloud 602 thatmay form in an exhaust system is shown. Fuel cloud 602 may receive fuelfrom fuel vapor storage canister 203 when the canister purge valve isopen as indicated by arrow 604. Fuel cloud 602 may also receive fuelfrom fuel injectors 66 as indicated by arrow 606. Fuel cloud 602 mayprovide fuel to exhaust after treatment device 70 as indicated by arrow608.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, atleast a portion of the described actions, operations and/or functionsmay graphically represent code to be programmed into non-transitorymemory of the computer readable storage medium in the control system.The control actions may also transform the operating state of one ormore sensors or actuators in the physical world when the describedactions are carried out by executing the instructions in a systemincluding the various engine hardware components in combination with oneor more controllers.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas,gasoline, diesel, or alternative fuel configurations could use thepresent description to advantage.

1. An engine operating method, comprising: operating an engine in a fuelcut-out mode wherein the engine rotates without injecting fuel to theengine via fuel injectors; delivering fuel to the engine via a fuelvapor canister while operating the engine in the fuel cut-out mode;estimating a temperature of an exhaust after treatment device via acontroller, the controller estimating the temperature of the exhaustafter treatment device based on combusting fuel supplied from the fuelvapor canister in the exhaust after treatment device while operating theengine in the fuel cut-out mode; delivering oxygen to the exhaust aftertreatment device during the fuel cut-out mode; exiting the fuel cut-outmode and reactivating the exhaust after treatment device via combustinga rich air-fuel ratio in the engine after delivering oxygen to theexhaust after treatment device during the fuel cut-out mode; reducing anamount of fuel injected to reactivate the exhaust after treatment devicein response to the temperature of the exhaust after treatment device;and adjusting a position of a throttle in response to the temperature,wherein estimating the temperature of the exhaust after treatment deviceincludes estimating an amount of fuel combusting in the exhaust aftertreatment device after leaving a fuel cloud during the fuel cut-outmode, wherein estimating the temperature is further based on a mass offuel supplied to reactivate the exhaust after treatment device. 2-3.(canceled)
 4. The method of claim 1, further comprising decreasing anopening amount of the purge control valve in response to the temperatureof the exhaust after treatment device exceeding a threshold temperature.5. (canceled)
 6. The method of claim 1, where the fuel cloud includesfuel supplied from the fuel vapor canister.
 7. The method of claim 1,further comprising estimating an amount of fuel stored in the fuelcloud.
 8. A system, comprising: an engine including a plurality ofcylinders having a plurality of fuel injectors and an after treatmentdevice; a canister including stored fuel vapors; a purge control valvein fluidic communication with the canister; and a controller includingexecutable instructions stored in non-transitory memory that cause thecontroller to adjust a position of the purge control valve whenoperating the engine in a fuel cut-out mode, and executable instructionsto adjust a position of a throttle and a puree control valve whileoperating in the fuel cut-out mode in response to an estimate of atemperature of the after treatment device while fuel vapors flow fromthe purge control valve to the after treatment device, wherein theestimate of the temperature of the after treatment device includesestimating an amount of fuel combusting in the after treatment deviceafter leaving a fuel cloud during the fuel cut-out mode, and where theestimate is further based on a mass of fuel supplied to reactivate theexhaust after treatment device.
 9. The system of claim 8, wherein thefuel vapors flow from the purge control valve to the after treatmentdevice via at least partially opening the purge control valve.
 10. Thesystem of claim 8, where the mass of fuel leaving the fuel cloud isbased on an air mass flow rate through an engine.
 11. The system ofclaim 10, where opening the purge control valve supplies fuel to thefuel cloud.
 12. The system of claim 8, where adjusting the position ofthe purge control valve includes closing the purge control valve inresponse to the estimate of the temperature being greater than athreshold temperature.
 13. The system of claim 8, further comprisingadditional instructions to estimate an amount of fuel being combustedvia the after treatment device.
 14. The system of claim 8, furthercomprising additional instructions to adjust an exotherm temperature inresponse to exiting a fuel vapor canister purge mode.
 15. An engineoperating method, comprising: operating an engine in a fuel cut-out modevia a controller wherein the engine rotates without injecting fuel tothe engine via fuel injectors; delivering fuel to the engine via a fuelvapor canister while operating the engine in the fuel cut-out mode;estimating an amount of fuel being delivered to the engine via the fuelvapor canister; estimating an amount of fuel stored in a fuel cloud, thefuel cloud containing fuel from the fuel vapor canister; estimating anamount of fuel exiting the fuel cloud and combusting in an exhaust aftertreatment device, where the amount of fuel exiting the fuel cloud isbased on an air mass flow rate through the engine; estimating atemperature of the exhaust after treatment device via the controller,the controller estimating the temperature of the exhaust after treatmentdevice based on the amount of fuel exiting the fuel cloud and beingcombusted in the exhaust after treatment device during the fuel cut-outmode; and adjusting a position of a throttle and a purge control valvein response to the temperature. 16-18. (canceled)
 19. The method ofclaim 15, further comprising: delivering oxygen to the exhaust aftertreatment device during the fuel cut-out mode; exiting the fuel cut-outmode and reactivating the exhaust after treatment device via combustinga rich air-fuel ratio in the engine after delivering oxygen to theexhaust after treatment device during the fuel cut-out mode; andreducing an amount of fuel injected to reactivate the exhaust aftertreatment device in response to the temperature of the exhaust aftertreatment device.
 20. The method of claim 19, further comprising closinga purge control valve in response to the amount of fuel being deliveredto the engine via the fuel vapor canister.